PROJECT SUMMARY/ABSTRACT There is a fundamental gap in understanding how best to de-implement health care practices that may have previously made sense, but because of new evidence, are no longer favorable. Acute bronchiolitis is a common lung disease of infants caused by respiratory viral infection. Continuous pulse oximetry monitoring in stable hospitalized infants with bronchiolitis is an overused practice that has persisted despite clinical practice guidelines and mounting evidence discouraging its use. Overuse of continuous pulse oximetry monitoring can prolong length of stay (which also elevates risk of suffering iatrogenic harm), increase costs, and contribute to alarm fatigue. The long term goal of the applicant is to better understand the strategies that are most effective for de-implementing low value care practices that have the potential to harm hospitalized children. The overall objective of this application is to gain a comprehensive understanding of pulse oximetry overuse and develop a multifaceted de-implementation strategy for continuous pulse oximetry monitoring in stable bronchiolitis patients not requiring supplemental oxygen. In this project, we will prepare for the Eliminating Monitor Overuse (EMO) Pulse Oximetry Trial, an effectiveness-implementation trial grounded in the Consolidated Framework for Implementation Research focused on de-implementing overuse of continuous pulse oximetry monitoring in bronchiolitis. The rationale for the proposed research is that evidence suggests pulse oximetry overuse occurs in nearly half of all infants with bronchiolitis for whom there is no monitoring indication, and there is high between-hospital variability in overuse. In this proposal we will pursue three Specific Aims: (1) Measure baseline pulse oximetry monitoring overuse rates in infants with bronchiolitis not requiring supplemental oxygen in Pediatric Research in Inpatient Settings Network hospitals, (2) Identify barriers and facilitators to de- implementing pulse oximetry monitoring by conducting semi-structured interviews with key stakeholders at the highest- and lowest-overuse hospitals, and (3) Develop a multifaceted de-implementation strategy for pulse oximetry monitoring overuse in infants with bronchiolitis not requiring supplemental oxygen that will serve as the intervention to be tested in a hybrid trial. This approach is innovative, in the applicant?s opinion, because it focuses on pediatric de-implementation, it is grounded in implementation science frameworks and behavioral theory, and it applies rigorous methods to developing de-implementation strategies in collaboration with physician, nurse, respiratory therapist, administrator, and parent stakeholders. The proposed research is significant because it is relevant to the 100,000 infants and children admitted with bronchiolitis each year. In addition, this project will advance implementation science by building a comprehensive understanding of barriers and facilitators to de-implementation in a pediatric population and leading directly to a hybrid trial to test a rigorously developed de-implementation strategy.